Syngas Production by Methane Reforming and H2 Purification by CO Abatement over Transition Metal-Substituted Reducible Oxides

Abstract

Methane and carbon dioxide are two major greenhouse gases, with CH4 having higher potency towards global warming. Several methods have been explored for transforming CH4 into higher value products, of which syngas production by steam reforming of methane (SRM) is found to be economically viable. Owing to the high concentration of H2 in SRM derived syngas, water-gas shift reaction (WGSR) is employed as a downstream process for H2 enrichment. Dry reforming of methane (DRM) is an alternate reforming process that is beneficial for reforming natural gas with high CO2 content. Supported-Ni catalysts, which have been extensively studied for methane reforming, suffer from severe deactivation due to coke deposition, active metal sintering or its irreversible reaction with the support. The dispersion of active metal, nature of support and metal-support interactions plays a vital role in designing catalysts for methane reforming. The ensemble size of the metal has a profound effect on the CH4 decomposition mechanism, which eventually determines the degree of carbon deposition. The present work focuses on developing metal-substituted catalysts in reducible oxides, which facilitates high ionic dispersion of active metal and enhancement in reducibility of the oxide. Bimetallic Ni-Pt substituted CoTiO3 have been studied for SRM and DRM. In another study, noble metal-substituted Ce-based pyrochlores have been studied for DRM. The involvement of support and its role in stabilizing surface intermediates have been studied to develop detailed mechanistic models over the synthesized materials. Water-gas shift reaction is an industrially important reaction for H2 enrichment post SRM reaction and the development of catalysts for single stage WGSR is desired to replace the conventional multi-shift process. In this study, WGSR has been studied over Pt and Cu modified NiTiO3. The interplay between metal and support has been established by the knowledge of surface intermediates and the involvement of lattice oxygen. Finally, the catalytic activity of noble metal substituted and supported on Fe2O3 was studied for CO oxidation. The superior activity of Fe2O3-supported noble metal over noble metal-substituted Fe2O3 demonstrates that the nature of defects is key to high catalytic activity metal-substituted catalyst.